Improved Light Output Power of GaN-Based Flip-Chip Light-Emitting Diode Through SiO2 Cones

We formed SiO2 cones on p-type GaN by using a simple wet-etching process and investigated the effects of the size and the coverage of the SiO2 cones on the output power performance of GaN-based light-emitting diodes (LEDs). The diameter of two different size SiO2 cones and the distance between the cones are in a range of 17.3-21.1 mu m and 32.7-33.9 mu m, respectively. The coverage of the SiO2 cones on p-type GaN is measured to be 9.5 - 10.9%. As the SiO2 cone size increases, LEDs exhibit a slightly higher forward-bias voltage (at an injection current of 20 mA) and somewhat higher series resistance. The light output increases with an increase in the size of the cones; the LEDs fabricated with the cones exhibit 5.8-8.4% higher light output power (at 20 mA) than those without the SiO2 cones.